/*
 * Copyright © 2017 eqxiu.com 北京中网易企秀科技有限公司  All rights reserved.
 */
package cn.hermit.core;

import cn.hermit.util.ReflectionUtils;

import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.Serializable;
import java.util.AbstractCollection;
import java.util.AbstractSet;
import java.util.Arrays;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;

/**
 * IdentityMap which can support duplicated Map keys.
 * 
 * <p>It is implemented by Array inside using hash location.</p>
 * 
 * @author Jack Gao (Chinese name : GAO JIANGUO, Email : linux.gjg@gmail.com)
 * @date 27 Jun, 2014
 */
@SuppressWarnings("unchecked")
public class IdentityHashMap<K, V> extends AbstractIdentityMap<K, V> implements
		Map<K, V>, Cloneable, Serializable {

	/**
	 * The default initial capacity - MUST be a power of two.
	 */
	static final int DEFAULT_INITIAL_CAPACITY = 1 << 4; // aka 16

	/**
	 * The maximum capacity, used if a higher value is implicitly specified by
	 * either of the constructors with arguments. MUST be a power of two <=
	 * 1<<30.
	 */
	static final int MAXIMUM_CAPACITY = 1 << 30;

	/**
	 * The load factor used when none specified in constructor.
	 */
	static final float DEFAULT_LOAD_FACTOR = 0.75f;

	/**
	 * An empty table instance to share when the table is not inflated.
	 */
	static final Entry<?, ?>[] EMPTY_TABLE = {};

	/**
	 * The table, resized as necessary. Length MUST Always be a power of two.
	 */
	transient Entry<K, V>[] table = (Entry<K, V>[]) EMPTY_TABLE;

	/**
	 * The number of key-value mappings contained in this map.
	 */
	transient int size;

	/**
	 * The next size value at which to resize (capacity * load factor).
	 * 
	 * @serial
	 */
	// If table == EMPTY_TABLE then this is the initial capacity at which the
	// table will be created when inflated.
	int threshold;

	/**
	 * The load factor for the hash table.
	 * 
	 * @serial
	 */
	final float loadFactor;

	/**
	 * The number of times this IdentityOrderedMap has been structurally
	 * modified Structural modifications are those that change the number of
	 * mappings in the IdentityOrderedMap or otherwise modify its internal
	 * structure (e.g., rehash). This field is used to make iterators on
	 * Collection-views of the IdentityOrderedMap fail-fast. (See
	 * ConcurrentModificationException).
	 */
	transient int modCount;

	/**
	 * The default threshold of map capacity above which alternative hashing is
	 * used for String keys. Alternative hashing reduces the incidence of
	 * collisions due to weak hash code calculation for String keys.
	 * <p/>
	 * This value may be overridden by defining the system property
	 * {@code jdk.map.althashing.threshold}. A property value of {@code 1}
	 * forces alternative hashing to be used at all times whereas {@code -1}
	 * value ensures that alternative hashing is never used.
	 */
	static final int ALTERNATIVE_HASHING_THRESHOLD_DEFAULT = Integer.MAX_VALUE;

	/**
	 * holds values which can't be initialized until after VM is booted.
	 */
	private static class Holder {

		/**
		 * Table capacity above which to switch to use alternative hashing.
		 */
		static final int ALTERNATIVE_HASHING_THRESHOLD;

		static {
			String altThreshold = java.security.AccessController
					.doPrivileged(new sun.security.action.GetPropertyAction(
							"jdk.map.althashing.threshold"));

			int threshold;
			try {
				threshold = (null != altThreshold) ? Integer
						.parseInt(altThreshold)
						: ALTERNATIVE_HASHING_THRESHOLD_DEFAULT;

				// disable alternative hashing if -1
				if (threshold == -1) {
					threshold = Integer.MAX_VALUE;
				}

				if (threshold < 0) {
					throw new IllegalArgumentException(
							"value must be positive integer.");
				}
			} catch (IllegalArgumentException failed) {
				throw new Error(
						"Illegal value for 'jdk.map.althashing.threshold'",
						failed);
			}

			ALTERNATIVE_HASHING_THRESHOLD = threshold;
		}
	}

	/**
	 * A randomizing value associated with this instance that is applied to hash
	 * code of keys to make hash collisions harder to find. If 0 then
	 * alternative hashing is disabled.
	 */
	transient int hashSeed = 0;

	/**
	 * Constructs an empty <tt>IdentityOrderedMap</tt> with the specified
	 * initial capacity and load factor.
	 * 
	 * @param initialCapacity
	 *            the initial capacity
	 * @param loadFactor
	 *            the load factor
	 * @throws IllegalArgumentException
	 *             if the initial capacity is negative or the load factor is
	 *             nonpositive
	 */
	public IdentityHashMap(int initialCapacity, float loadFactor) {
		if (initialCapacity < 0)
			throw new IllegalArgumentException("Illegal initial capacity: "
					+ initialCapacity);
		if (initialCapacity > MAXIMUM_CAPACITY)
			initialCapacity = MAXIMUM_CAPACITY;
		if (loadFactor <= 0 || Float.isNaN(loadFactor))
			throw new IllegalArgumentException("Illegal load factor: "
					+ loadFactor);

		this.loadFactor = loadFactor;
		threshold = initialCapacity;
		init();
	}

	/**
	 * Constructs an empty <tt>IdentityOrderedMap</tt> with the specified
	 * initial capacity and the default load factor (0.75).
	 * 
	 * @param initialCapacity
	 *            the initial capacity.
	 * @throws IllegalArgumentException
	 *             if the initial capacity is negative.
	 */
	public IdentityHashMap(int initialCapacity) {
		this(initialCapacity, DEFAULT_LOAD_FACTOR);
	}

	/**
	 * Constructs an empty <tt>IdentityOrderedMap</tt> with the default initial
	 * capacity (16) and the default load factor (0.75).
	 */
	public IdentityHashMap() {
		this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR);
	}

	/**
	 * Constructs a new <tt>IdentityOrderedMap</tt> with the same mappings as
	 * the specified <tt>Map</tt>. The <tt>IdentityOrderedMap</tt> is created
	 * with default load factor (0.75) and an initial capacity sufficient to
	 * hold the mappings in the specified <tt>Map</tt>.
	 * 
	 * @param m
	 *            the map whose mappings are to be placed in this map
	 * @throws NullPointerException
	 *             if the specified map is null
	 */
	public IdentityHashMap(Map<? extends K, ? extends V> m) {
		this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1,
				DEFAULT_INITIAL_CAPACITY), DEFAULT_LOAD_FACTOR);
		inflateTable(threshold);

		putAllForCreate(m);
	}

	private static int roundUpToPowerOf2(int number) {
		// assert number >= 0 : "number must be non-negative";
		int rounded = number >= MAXIMUM_CAPACITY ? MAXIMUM_CAPACITY
				: (rounded = Integer.highestOneBit(number)) != 0 ? (Integer
						.bitCount(number) > 1) ? rounded << 1 : rounded : 1;

		return rounded;
	}

	/**
	 * Inflates the table.
	 */
	private void inflateTable(int toSize) {
		// Find a power of 2 >= toSize
		int capacity = roundUpToPowerOf2(toSize);

		threshold = (int) Math.min(capacity * loadFactor, MAXIMUM_CAPACITY + 1);
		table = new Entry[capacity];
		initHashSeedAsNeeded(capacity);
	}

	// internal utilities

	/**
	 * Initialization hook for subclasses. This method is called in all
	 * constructors and pseudo-constructors (clone, readObject) after
	 * IdentityOrderedMap has been initialized but before any entries have been
	 * inserted. (In the absence of this method, readObject would require
	 * explicit knowledge of subclasses.)
	 */
	void init() {
	}

	/**
	 * Initialize the hashing mask value. We defer initialization until we
	 * really need it.
	 */
	final boolean initHashSeedAsNeeded(int capacity) {
		boolean currentAltHashing = hashSeed != 0;
		boolean useAltHashing = capacity >= Holder.ALTERNATIVE_HASHING_THRESHOLD;
		boolean switching = currentAltHashing ^ useAltHashing;
		if (switching) {
			hashSeed = 0;
		}
		return switching;
	}

	/**
	 * Returns index for Object x.
	 */
	protected int hash(Object x) {
		int length = table.length;
		int h = System.identityHashCode(x);
		// Multiply by -127, and left-shift to use least bit as part of hash
		return ((h << 1) - (h << 8)) & (length - 1);
	}

	/**
	 * Returns index for hash code h.
	 */
	static int indexFor(int h, int length) {
		// assert Integer.bitCount(length) == 1 :
		// "length must be a non-zero power of 2";
		return h & (length - 1);
	}

	/**
	 * Returns the number of key-value mappings in this map.
	 * 
	 * @return the number of key-value mappings in this map
	 */
	public int size() {
		return size;
	}

	/**
	 * Returns <tt>true</tt> if this map contains no key-value mappings.
	 * 
	 * @return <tt>true</tt> if this map contains no key-value mappings
	 */
	public boolean isEmpty() {
		return size == 0;
	}

	/**
	 * Returns the value to which the specified key is mapped, or {@code null}
	 * if this map contains no mapping for the key.
	 * 
	 * <p>
	 * More formally, if this map contains a mapping from a key {@code k} to a
	 * value {@code v} such that {@code (key==null ? k==null :
	 * key.equals(k))}, then this method returns {@code v}; otherwise it returns
	 * {@code null}. (There can be at most one such mapping.)
	 * 
	 * <p>
	 * A return value of {@code null} does not <i>necessarily</i> indicate that
	 * the map contains no mapping for the key; it's also possible that the map
	 * explicitly maps the key to {@code null}. The {@link #containsKey
	 * containsKey} operation may be used to distinguish these two cases.
	 * 
	 * @see #put(Object, Object)
	 */
	public V get(Object key) {
		if (key == null)
			return getForNullKey();
		Entry<K, V> entry = getEntry(key);

		return null == entry ? null : entry.getValue();
	}

	/**
	 * Offloaded version of get() to look up null keys. Null keys map to index
	 * 0. This null case is split out into separate methods for the sake of
	 * performance in the two most commonly used operations (get and put), but
	 * incorporated with conditionals in others.
	 */
	private V getForNullKey() {
		if (size == 0) {
			return null;
		}
		for (Entry<K, V> e = table[0]; e != null; e = e.next) {
			if (e.key == null)
				return e.value;
		}
		return null;
	}

	/**
	 * Returns <tt>true</tt> if this map contains a mapping for the specified
	 * key.
	 * 
	 * @param key
	 *            The key whose presence in this map is to be tested
	 * @return <tt>true</tt> if this map contains a mapping for the specified
	 *         key.
	 */
	public boolean containsKey(Object key) {
		return getEntry(key) != null;
	}

	/**
	 * Returns the entry associated with the specified key in the
	 * IdentityOrderedMap. Returns null if the IdentityOrderedMap contains no
	 * mapping for the key.
	 */
	final Entry<K, V> getEntry(Object key) {
		if (size == 0) {
			return null;
		}

		int hash = (key == null) ? 0 : hash(key);
		for (Entry<K, V> e = table[indexFor(hash, table.length)]; e != null; e = e.next) {
			Object k;
			if (e.hash == hash
					&& ((k = e.key) == key || (key != null && key.equals(k))))
				return e;
		}
		return null;
	}

	/**
	 * Associates the specified value with the specified key in this map. If the
	 * map previously contained a mapping for the key, the old value is
	 * replaced.
	 * 
	 * @param key
	 *            key with which the specified value is to be associated
	 * @param value
	 *            value to be associated with the specified key
	 * @return the previous value associated with <tt>key</tt>, or <tt>null</tt>
	 *         if there was no mapping for <tt>key</tt>. (A <tt>null</tt> return
	 *         can also indicate that the map previously associated
	 *         <tt>null</tt> with <tt>key</tt>.)
	 */
	public V put(K key, V value) {
		if (table == EMPTY_TABLE) {
			inflateTable(threshold);
		}
		key = (K) ReflectionUtils.getNoCacheObject(key);
		if (key == null)
			return putForNullKey(value);
		int hash = hash(key);
		int i = indexFor(hash, table.length);
		for (Entry<K, V> e = table[i]; e != null; e = e.next) {
			if (e.hash == hash && (e.key == key)) {
				V oldValue = e.value;
				e.value = value;
				e.recordAccess(this);
				return oldValue;
			}
		}

		modCount++;
		addEntry(hash, key, value, i);
		return null;
	}

	/**
	 * Offloaded version of put for null keys
	 */
	private V putForNullKey(V value) {
		for (Entry<K, V> e = table[0]; e != null; e = e.next) {
			if (e.key == null) {
				V oldValue = e.value;
				e.value = value;
				e.recordAccess(this);
				return oldValue;
			}
		}
		modCount++;
		addEntry(0, null, value, 0);
		return null;
	}

	/**
	 * This method is used instead of put by constructors and pseudoconstructors
	 * (clone, readObject). It does not resize the table, check for
	 * comodification, etc. It calls createEntry rather than addEntry.
	 */
	private void putForCreate(K key, V value) {
		int hash = null == key ? 0 : hash(key);
		int i = indexFor(hash, table.length);

		/**
		 * Look for preexisting entry for key. This will never happen for clone
		 * or deserialize. It will only happen for construction if the input Map
		 * is a sorted map whose ordering is inconsistent w/ equals.
		 */
		for (Entry<K, V> e = table[i]; e != null; e = e.next) {
			Object k;
			if (e.hash == hash
					&& ((k = e.key) == key || (key != null && key.equals(k)))) {
				e.value = value;
				return;
			}
		}

		createEntry(hash, key, value, i);
	}

	private void putAllForCreate(Map<? extends K, ? extends V> m) {
		for (Map.Entry<? extends K, ? extends V> e : m.entrySet())
			putForCreate(e.getKey(), e.getValue());
	}

	/**
	 * Rehashes the contents of this map into a new array with a larger
	 * capacity. This method is called automatically when the number of keys in
	 * this map reaches its threshold.
	 * 
	 * If current capacity is MAXIMUM_CAPACITY, this method does not resize the
	 * map, but sets threshold to Integer.MAX_VALUE. This has the effect of
	 * preventing future calls.
	 * 
	 * @param newCapacity
	 *            the new capacity, MUST be a power of two; must be greater than
	 *            current capacity unless current capacity is MAXIMUM_CAPACITY
	 *            (in which case value is irrelevant).
	 */
	void resize(int newCapacity) {
		Entry<K, V>[] oldTable = table;
		int oldCapacity = oldTable.length;
		if (oldCapacity == MAXIMUM_CAPACITY) {
			threshold = Integer.MAX_VALUE;
			return;
		}

		Entry<K, V>[] newTable = new Entry[newCapacity];
		transfer(newTable, initHashSeedAsNeeded(newCapacity));
		table = newTable;
		threshold = (int) Math.min(newCapacity * loadFactor,
				MAXIMUM_CAPACITY + 1);
	}

	/**
	 * Transfers all entries from current table to newTable.
	 */
	void transfer(Entry<K, V>[] newTable, boolean rehash) {
		int newCapacity = newTable.length;
		for (Entry<K, V> e : table) {
			while (null != e) {
				Entry<K, V> next = e.next;
				if (rehash) {
					e.hash = null == e.key ? 0 : hash(e.key);
				}
				int i = indexFor(e.hash, newCapacity);
				e.next = newTable[i];
				newTable[i] = e;
				e = next;
			}
		}
	}

	/**
	 * Copies all of the mappings from the specified map to this map. These
	 * mappings will replace any mappings that this map had for any of the keys
	 * currently in the specified map.
	 * 
	 * @param m
	 *            mappings to be stored in this map
	 * @throws NullPointerException
	 *             if the specified map is null
	 */
	public void putAll(Map<? extends K, ? extends V> m) {
		int numKeysToBeAdded = m.size();
		if (numKeysToBeAdded == 0)
			return;

		if (table == EMPTY_TABLE) {
			inflateTable((int) Math.max(numKeysToBeAdded * loadFactor,
					threshold));
		}

		/*
		 * Expand the map if the map if the number of mappings to be added is
		 * greater than or equal to threshold. This is conservative; the obvious
		 * condition is (m.size() + size) >= threshold, but this condition could
		 * result in a map with twice the appropriate capacity, if the keys to
		 * be added overlap with the keys already in this map. By using the
		 * conservative calculation, we subject ourself to at most one extra
		 * resize.
		 */
		if (numKeysToBeAdded > threshold) {
			int targetCapacity = (int) (numKeysToBeAdded / loadFactor + 1);
			if (targetCapacity > MAXIMUM_CAPACITY)
				targetCapacity = MAXIMUM_CAPACITY;
			int newCapacity = table.length;
			while (newCapacity < targetCapacity)
				newCapacity <<= 1;
			if (newCapacity > table.length)
				resize(newCapacity);
		}

		for (Map.Entry<? extends K, ? extends V> e : m.entrySet())
			put(e.getKey(), e.getValue());
	}

	/**
	 * Removes the mapping for the specified key from this map if present.
	 * 
	 * @param key
	 *            key whose mapping is to be removed from the map
	 * @return the previous value associated with <tt>key</tt>, or <tt>null</tt>
	 *         if there was no mapping for <tt>key</tt>. (A <tt>null</tt> return
	 *         can also indicate that the map previously associated
	 *         <tt>null</tt> with <tt>key</tt>.)
	 */
	public V remove(Object key) {
		Entry<K, V> e = removeEntryForKey(key);
		return (e == null ? null : e.value);
	}

	/**
	 * Removes and returns the entry associated with the specified key in the
	 * IdentityOrderedMap. Returns null if the IdentityOrderedMap contains no
	 * mapping for this key.
	 */
	final Entry<K, V> removeEntryForKey(Object key) {
		if (size == 0) {
			return null;
		}
		int hash = (key == null) ? 0 : hash(key);
		int i = indexFor(hash, table.length);
		Entry<K, V> prev = table[i];
		Entry<K, V> e = prev;

		while (e != null) {
			Entry<K, V> next = e.next;
			Object k;
			if (e.hash == hash
					&& ((k = e.key) == key || (key != null && key.equals(k)))) {
				modCount++;
				size--;
				if (prev == e)
					table[i] = next;
				else
					prev.next = next;
				e.recordRemoval(this);
				return e;
			}
			prev = e;
			e = next;
		}

		return e;
	}

	/**
	 * Special version of remove for EntrySet using {@code Map.Entry.equals()}
	 * for matching.
	 */
	final Entry<K, V> removeMapping(Object o) {
		if (size == 0 || !(o instanceof Map.Entry))
			return null;

		Map.Entry<K, V> entry = (Map.Entry<K, V>) o;
		Object key = entry.getKey();
		int hash = (key == null) ? 0 : hash(key);
		int i = indexFor(hash, table.length);
		Entry<K, V> prev = table[i];
		Entry<K, V> e = prev;

		while (e != null) {
			Entry<K, V> next = e.next;
			if (e.hash == hash && e.equals(entry)) {
				modCount++;
				size--;
				if (prev == e)
					table[i] = next;
				else
					prev.next = next;
				e.recordRemoval(this);
				return e;
			}
			prev = e;
			e = next;
		}

		return e;
	}

	/**
	 * Removes all of the mappings from this map. The map will be empty after
	 * this call returns.
	 */
	public void clear() {
		modCount++;
		Arrays.fill(table, null);
		size = 0;
	}

	/**
	 * Returns <tt>true</tt> if this map maps one or more keys to the specified
	 * value.
	 * 
	 * @param value
	 *            value whose presence in this map is to be tested
	 * @return <tt>true</tt> if this map maps one or more keys to the specified
	 *         value
	 */
	public boolean containsValue(Object value) {
		if (value == null)
			return containsNullValue();

		Entry<K, V>[] tab = table;
		for (int i = 0; i < tab.length; i++)
			for (Entry<K, V> e = tab[i]; e != null; e = e.next)
				if (value.equals(e.value))
					return true;
		return false;
	}

	/**
	 * Special-case code for containsValue with null argument
	 */
	private boolean containsNullValue() {
		Entry<K, V>[] tab = table;
		for (int i = 0; i < tab.length; i++)
			for (Entry<K, V> e = tab[i]; e != null; e = e.next)
				if (e.value == null)
					return true;
		return false;
	}

	/**
	 * Returns a shallow copy of this <tt>IdentityOrderedMap</tt> instance: the
	 * keys and values themselves are not cloned.
	 * 
	 * @return a shallow copy of this map
	 */
	public Object clone() {
		IdentityHashMap<K, V> result = null;
		try {
			result = (IdentityHashMap<K, V>) super.clone();
		} catch (CloneNotSupportedException e) {
			// assert false;
		}
		if (result.table != EMPTY_TABLE) {
			result.inflateTable(Math.min(
					(int) Math.min(size * Math.min(1 / loadFactor, 4.0f),
					// we have limits...
							IdentityHashMap.MAXIMUM_CAPACITY), table.length));
		}
		result.entrySet = null;
		result.modCount = 0;
		result.size = 0;
		result.init();
		result.putAllForCreate(this);

		return result;
	}

	static class Entry<K, V> implements Map.Entry<K, V> {
		final K key;
		V value;
		Entry<K, V> next;
		int hash;

		/**
		 * Creates new entry.
		 */
		Entry(int h, K k, V v, Entry<K, V> n) {
			value = v;
			next = n;
			key = k;
			hash = h;
		}

		public final K getKey() {
			return key;
		}

		public final V getValue() {
			return value;
		}

		public final V setValue(V newValue) {
			V oldValue = value;
			value = newValue;
			return oldValue;
		}

		public final boolean equals(Object o) {
			if (!(o instanceof Map.Entry))
				return false;
			Entry<K, V> e = (Entry<K, V>) o;
			Object k1 = getKey();
			Object k2 = e.getKey();
			if (k1 == k2 || (k1 != null && k1.equals(k2))) {
				Object v1 = getValue();
				Object v2 = e.getValue();
				if (v1 == v2 || (v1 != null && v1.equals(v2)))
					return true;
			}
			return false;
		}

		public final int hashCode() {
			return System.identityHashCode(getKey()) ^ System.identityHashCode(getValue());
		}

		public final String toString() {
			return getKey() + "=" + getValue();
		}

		/**
		 * This method is invoked whenever the value in an entry is overwritten
		 * by an invocation of put(k,v) for a key k that's already in the
		 * IdentityOrderedMap.
		 */
		void recordAccess(IdentityHashMap<K, V> m) {
		}

		/**
		 * This method is invoked whenever the entry is removed from the table.
		 */
		void recordRemoval(IdentityHashMap<K, V> m) {
		}
	}

	/**
	 * Adds a new entry with the specified key, value and hash code to the
	 * specified bucket. It is the responsibility of this method to resize the
	 * table if appropriate.
	 * 
	 * Subclass overrides this to alter the behavior of put method.
	 */
	void addEntry(int hash, K key, V value, int bucketIndex) {
		if ((size >= threshold) && (null != table[bucketIndex])) {
			resize(2 * table.length);
			hash = (null != key) ? hash(key) : 0;
			bucketIndex = indexFor(hash, table.length);
		}

		createEntry(hash, key, value, bucketIndex);
	}

	/**
	 * Like addEntry except that this version is used when creating entries as
	 * part of Map construction or "pseudo-construction" (cloning,
	 * deserialization). This version needn't worry about resizing the table.
	 * 
	 * Subclass overrides this to alter the behavior of IdentityOrderedMap(Map),
	 * clone, and readObject.
	 */
	void createEntry(int hash, K key, V value, int bucketIndex) {
		Entry<K, V> e = table[bucketIndex];
		table[bucketIndex] = new Entry<K, V>(hash, key, value, e);
		size++;
	}

	private abstract class HashIterator<E> implements Iterator<E> {
		Entry<K, V> next; // next entry to return
		int expectedModCount; // For fast-fail
		int index; // current slot
		Entry<K, V> current; // current entry

		HashIterator() {
			expectedModCount = modCount;
			if (size > 0) { // advance to first entry
				Entry<K, V>[] t = table;
				while (index < t.length && (next = t[index++]) == null)
					;
			}
		}

		public final boolean hasNext() {
			return next != null;
		}

		final Entry<K, V> nextEntry() {
			if (modCount != expectedModCount)
				throw new ConcurrentModificationException();
			Entry<K, V> e = next;
			if (e == null)
				throw new NoSuchElementException();

			if ((next = e.next) == null) {
				Entry<K, V>[] t = table;
				while (index < t.length && (next = t[index++]) == null)
					;
			}
			current = e;
			return e;
		}

		public void remove() {
			if (current == null)
				throw new IllegalStateException();
			if (modCount != expectedModCount)
				throw new ConcurrentModificationException();
			Object k = current.key;
			current = null;
			IdentityHashMap.this.removeEntryForKey(k);
			expectedModCount = modCount;
		}
	}

	private final class ValueIterator extends HashIterator<V> {
		public V next() {
			return nextEntry().value;
		}
	}

	private final class KeyIterator extends HashIterator<K> {
		public K next() {
			return nextEntry().getKey();
		}
	}

	private final class EntryIterator extends HashIterator<Map.Entry<K, V>> {
		public Map.Entry<K, V> next() {
			return nextEntry();
		}
	}

	// Subclass overrides these to alter behavior of views' iterator() method
	Iterator<K> newKeyIterator() {
		return new KeyIterator();
	}

	Iterator<V> newValueIterator() {
		return new ValueIterator();
	}

	Iterator<Map.Entry<K, V>> newEntryIterator() {
		return new EntryIterator();
	}

	// Views

	private transient Set<Map.Entry<K, V>> entrySet = null;

	/**
	 * Returns a {@link Set} view of the keys contained in this map. The setHeader is
	 * backed by the map, so changes to the map are reflected in the setHeader, and
	 * vice-versa. If the map is modified while an iteration over the setHeader is in
	 * progress (except through the iterator's own <tt>remove</tt> operation),
	 * the results of the iteration are undefined. The setHeader supports element
	 * removal, which removes the corresponding mapping from the map, via the
	 * <tt>Iterator.remove</tt>, <tt>Set.remove</tt>, <tt>removeAll</tt>,
	 * <tt>retainAll</tt>, and <tt>clear</tt> operations. It does not support
	 * the <tt>add</tt> or <tt>addAll</tt> operations.
	 */
	public Set<K> keySet() {
		Set<K> ks = keySet;
		return (ks != null ? ks : (keySet = new KeySet()));
	}

	private final class KeySet extends AbstractSet<K> {
		public Iterator<K> iterator() {
			return newKeyIterator();
		}

		public int size() {
			return size;
		}

		public boolean contains(Object o) {
			return containsKey(o);
		}

		public boolean remove(Object o) {
			return IdentityHashMap.this.removeEntryForKey(o) != null;
		}

		public void clear() {
			IdentityHashMap.this.clear();
		}
	}

	/**
	 * Returns a {@link Collection} view of the values contained in this map.
	 * The collection is backed by the map, so changes to the map are reflected
	 * in the collection, and vice-versa. If the map is modified while an
	 * iteration over the collection is in progress (except through the
	 * iterator's own <tt>remove</tt> operation), the results of the iteration
	 * are undefined. The collection supports element removal, which removes the
	 * corresponding mapping from the map, via the <tt>Iterator.remove</tt>,
	 * <tt>Collection.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and
	 * <tt>clear</tt> operations. It does not support the <tt>add</tt> or
	 * <tt>addAll</tt> operations.
	 */
	public Collection<V> values() {
		Collection<V> vs = values;
		return (vs != null ? vs : (values = new Values()));
	}

	private final class Values extends AbstractCollection<V> {
		public Iterator<V> iterator() {
			return newValueIterator();
		}

		public int size() {
			return size;
		}

		public boolean contains(Object o) {
			return containsValue(o);
		}

		public void clear() {
			IdentityHashMap.this.clear();
		}
	}

	/**
	 * Returns a {@link Set} view of the mappings contained in this map. The setHeader
	 * is backed by the map, so changes to the map are reflected in the setHeader, and
	 * vice-versa. If the map is modified while an iteration over the setHeader is in
	 * progress (except through the iterator's own <tt>remove</tt> operation, or
	 * through the <tt>setValue</tt> operation on a map entry returned by the
	 * iterator) the results of the iteration are undefined. The setHeader supports
	 * element removal, which removes the corresponding mapping from the map,
	 * via the <tt>Iterator.remove</tt>, <tt>Set.remove</tt>, <tt>removeAll</tt>
	 * , <tt>retainAll</tt> and <tt>clear</tt> operations. It does not support
	 * the <tt>add</tt> or <tt>addAll</tt> operations.
	 * 
	 * @return a setHeader view of the mappings contained in this map
	 */
	public Set<Map.Entry<K, V>> entrySet() {
		return entrySet0();
	}

	private Set<Map.Entry<K, V>> entrySet0() {
		Set<Map.Entry<K, V>> es = entrySet;
		return es != null ? es : (entrySet = new EntrySet());
	}

	private final class EntrySet extends AbstractSet<Map.Entry<K, V>> {
		public Iterator<Map.Entry<K, V>> iterator() {
			return newEntryIterator();
		}

		public boolean contains(Object o) {
			if (!(o instanceof Map.Entry))
				return false;
			Map.Entry<K, V> e = (Map.Entry<K, V>) o;
			Entry<K, V> candidate = getEntry(e.getKey());
			return candidate != null && candidate.equals(e);
		}

		public boolean remove(Object o) {
			return removeMapping(o) != null;
		}

		public int size() {
			return size;
		}

		public void clear() {
			IdentityHashMap.this.clear();
		}
	}

	/**
	 * Save the state of the <tt>IdentityOrderedMap</tt> instance to a stream
	 * (i.e., serialize it).
	 * 
	 * @serialData The <i>capacity</i> of the IdentityOrderedMap (the length of
	 *             the bucket array) is emitted (int), followed by the
	 *             <i>size</i> (an int, the number of key-value mappings),
	 *             followed by the key (Object) and value (Object) for each
	 *             key-value mapping. The key-value mappings are emitted in no
	 *             particular order.
	 */
	private void writeObject(java.io.ObjectOutputStream s) throws IOException {
		// Write out the threshold, loadfactor, and any hidden stuff
		s.defaultWriteObject();

		// Write out number of buckets
		if (table == EMPTY_TABLE) {
			s.writeInt(roundUpToPowerOf2(threshold));
		} else {
			s.writeInt(table.length);
		}

		// Write out size (number of Mappings)
		s.writeInt(size);

		// Write out keys and values (alternating)
		if (size > 0) {
			for (Map.Entry<K, V> e : entrySet0()) {
				s.writeObject(e.getKey());
				s.writeObject(e.getValue());
			}
		}
	}

	private static final long serialVersionUID = 362498820763181265L;

	/**
	 * Reconstitute the {@code IdentityOrderedMap} instance from a stream (i.e.,
	 * deserialize it).
	 */
	private void readObject(java.io.ObjectInputStream s) throws IOException,
			ClassNotFoundException {
		// Read in the threshold (ignored), loadfactor, and any hidden stuff
		s.defaultReadObject();
		if (loadFactor <= 0 || Float.isNaN(loadFactor)) {
			throw new InvalidObjectException("Illegal load factor: "
					+ loadFactor);
		}

		// setHeader other fields that need values
		table = (Entry<K, V>[]) EMPTY_TABLE;

		// Read in number of buckets
		s.readInt(); // ignored.

		// Read number of mappings
		int mappings = s.readInt();
		if (mappings < 0)
			throw new InvalidObjectException("Illegal mappings count: "
					+ mappings);

		// capacity chosen by number of mappings and desired load (if >= 0.25)
		int capacity = (int) Math.min(
				mappings * Math.min(1 / loadFactor, 4.0f),
				// we have limits...
				MAXIMUM_CAPACITY);

		// allocate the bucket array;
		if (mappings > 0) {
			inflateTable(capacity);
		} else {
			threshold = capacity;
		}

		init(); // Give subclass a chance to do its thing.

		// Read the keys and values, and put the mappings in the
		// IdentityOrderedMap
		for (int i = 0; i < mappings; i++) {
			K key = (K) s.readObject();
			V value = (V) s.readObject();
			putForCreate(key, value);
		}
	}

	// These methods are used when serializing HashSets
	int capacity() {
		return table.length;
	}

	float loadFactor() {
		return loadFactor;
	}
}